1. Technical Field of the Invention
This invention relates to a liquid crystal display cell and, more particularly, to a liquid crystal display cell having a plurality of kinds of supporting members to keep spaces or gaps defined between two separate substrates.
2. Related Art
A liquid crystal display cell holds a liquid crystal layer in a gap defined between upper and lower substrates. In a conventional method of manufacturing such a liquid crystal display cell, the two substrates are sealed at the periphery thereof by a sealing material or sealant and a liquid crystal material is put into the cell through a liquid crystal injection inlet. The substrates of the cell are then pushed under the pressure applied to the substrates to discharge superfluous quantity of the liquid crystal material from the cell through the injection inlet. An end seal or a confining material is sucked up and hardens to close the injection inlet as the pressure is decreased or removed from the substrates.
In such a liquid crystal display cell, spacers are provided in the gap to define the distance between the upper and lower substrates in order to control the crystal layer thickness and to keep display quality good. There are ball-like silica or polyethylene spacers, pole-like spacers formed on the substrate through various patterning processes (see Japanese Laid-open Patent Applications Sho 59-139018 and Hei 5-196946) and the like. Since a liquid crystal display cell with the pole-like spacers has an advantage in less light leakage than one with the ball-like spacers has in the display region due to extraordinary alignment formed around the surroundings thereof. Demands for the latter are, thus, increasing.
As shown in FIG. 6, the pole-like spacers 12b and 12d, for instance, are formed and disposed on the light blocking layers (black matrix layers) 13a through 13d on a glass substrate 1 by means of the patterning processes. In order to control the liquid crystal layer thickness, the spacers 12a and 12d are about 5 .mu.m in height. Fixed diameter ball-like spacers are also used for the same purpose. Regions BM and P in the drawings show light blocking and pixel portions, respectively.
The same height spacers or same diameter spacers are used to control the liquid crystal layer thickness. In this case, however, as shown in FIGS. 7 and 8, the end seal 14 is sucked up after the unnecessary quantity of the liquid crystal has been discharged from the injection inlet of the cell and the pressure has been decreased or removed from the substrates. The sucked width or depth 6 of the end seal 14 is in proportion to the pressure applied to the substrates which have been fixed together by the sealant 15. Although the sucked width 6 of the end seal depends on liquid crystal display cells, it is necessary to make it about 1.0 mm from view points of strength and the like of the confining portion 16. As shown in characteristic curves (a) and (b) in FIG. 8, a pressure range to make the width proper (0.8 mm through 1.2 mm in a given example) is so limited that the pressure (magnitude and distribution) applied to the cell must be set up strictly. If the pressure state is changed due to positioning jigs used for application of the pressure, the sucked width .delta. is easily subject to fluctuation of the pressure. When the width .delta. is smaller than 0.8 mm, the cell lacks of the strength, the leakage of the liquid crystal material therefrom takes place, the production yield thereof becomes low, and the durability thereof also becomes poor. When the width .delta. is greater than 1.2 mm, the end seal is put into the display region so that it brings about an improper display.
It is important to suppress the problems due to the width change as set forth above. If the number of spacers is increased as for spacers 12a through 12d in FIG. 9 or for ball-like spacers, a possibly loaded pressure to the substrates does not furnish a sufficiently sucked width of the end seal as shown in a curve (c) of FIG. 8. A liquid crystal display cell with a satisfactory strength cannot be necessarily produced.